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by Jason.Jonkman
Thu May 13, 2021 5:25 pm
Forum: Computer-Aided Engineering Software Tools
Topic: FF wind array boundaries violated
Replies: 2
Views: 13

Re: FF wind array boundaries violated

Dear Atinuke, The error is being triggered because the position of an aerodynamic analysis node is NaN (Not a Number). This suggests that your model has gone numerically unstable, resulting in unrealistically large motions. It looks like the simulation failed about 50 s in; I would guess you are see...
by Jason.Jonkman
Thu May 13, 2021 3:55 pm
Forum: Computer-Aided Engineering Software Tools
Topic: The frequency component of flapwise
Replies: 15
Views: 3061

Re: The frequency component of flapwise

Dear Feng, The hydrostatic stiffness matrix (CH in your example) includes the effects of waterplane area and center of buoyancy, but it does not include the effects of full system body mass and center of mass. The full system mass matrix linked in the forum topic linked above (M in your example) inc...
by Jason.Jonkman
Thu May 13, 2021 2:56 pm
Forum: Computer-Aided Engineering Software Tools
Topic: The frequency component of flapwise
Replies: 15
Views: 3061

Re: The frequency component of flapwise

Dear Feng,

I see the problem. I don't see that you've included the restoring in roll and pitch associated with the influence of the full system body weight / center of mass. Effectively, you must add to KT(4,4) the contribution of gravity*M(2,4); likewise for KT(5,5).

Best regards,
by Jason.Jonkman
Thu May 13, 2021 6:30 am
Forum: Rotor Aerodynamics
Topic: Local angle of attack computation
Replies: 5
Views: 99

Re: Local angle of attack computation

Sounds reasonable.

Best regards,
by Jason.Jonkman
Thu May 13, 2021 6:28 am
Forum: General
Topic: FAST.Farm
Replies: 205
Views: 24894

Re: FAST.Farm

Dear Younes, Sometimes the debugger has problems viewing variables that are part of complex data types such as u%. I see that the local variables CosTerm and dp are computed correctly even though u%xhat_plane and u%p_plane are not viewable by the debugger (all of the inputs to AWAE, u%, are set to 0...
by Jason.Jonkman
Wed May 12, 2021 4:09 pm
Forum: Computer-Aided Engineering Software Tools
Topic: The frequency component of flapwise
Replies: 15
Views: 3061

Re: The frequency component of flapwise

Dear Feng, Your equation for the natural frequencies above applied to mass and stiffness values written as scalars (or only consider separate terms uncoupled). How are you calculating the natural frequencies with 6x6 matrices? Are you forming the first-order state-space matrix (A) and computing its ...
by Jason.Jonkman
Wed May 12, 2021 3:17 pm
Forum: Computer-Aided Engineering Software Tools
Topic: The frequency component of flapwise
Replies: 15
Views: 3061

Re: The frequency component of flapwise

Dear Feng, Yes, that is the correct full-system mass matrix. Have you now included the coupling between platform DOFs (off-diagonal terms in the matrices, including surge-pitch and sway-roll)--not just for the mass matrix, but also for the added mass matrix and mooring stiffness matrix? Best regards,
by Jason.Jonkman
Wed May 12, 2021 1:52 pm
Forum: Computer-Aided Engineering Software Tools
Topic: The frequency component of flapwise
Replies: 15
Views: 3061

Re: The frequency component of flapwise

Dear Feng, I agree with your numbers, but you seem to be missing three important effects: ⋅ The influence of the platform center of mass (from (0,0,0) on the roll and pitch inertia of platform; ⋅ The influence of the supported wind turbine mass, center of mass, and inertia; and &...
by Jason.Jonkman
Wed May 12, 2021 8:37 am
Forum: General
Topic: FAST.Farm
Replies: 205
Views: 24894

Re: FAST.Farm

Dear Younes, It looks like we responded at the same time; I see now that you can compile in debug mode. It is now telling you which line in the source code is causing the failure (line 137 of SUBROUTINE ComputeLocals() in AWAE.f90 , during the initial call to SUBROUTINE AWAE_CalcOutput()0. It is not...
by Jason.Jonkman
Wed May 12, 2021 6:51 am
Forum: General
Topic: FAST.Farm
Replies: 205
Views: 24894

Re: FAST.Farm

Dear Younes, The Echo variable is a way to debug problems with the formatting of an input file. But you don't seem to have a problem with your input file formats. From my brief look, I'm not seeing any problems with your input settings. I'm not aware of any issue running FAST.Farm with Mod_AmbWind =...
by Jason.Jonkman
Tue May 11, 2021 11:43 am
Forum: Rotor Aerodynamics
Topic: Local angle of attack computation
Replies: 5
Views: 99

Re: Local angle of attack computation

Dear Matteo,

OK, thanks for clarifying.

I have more experience with UAMod = 3 and little experience with UAMod = 2, but in your case, it looks like UAMod = 2 and UAMod = 3 are very similar (some differences are seen in Cd and Cm, but the values are quite small).

Best regards,
by Jason.Jonkman
Tue May 11, 2021 9:36 am
Forum: General
Topic: FAST.Farm
Replies: 205
Views: 24894

Re: FAST.Farm

Dear Jundong, I thought Younes answered your question regarding TwrShadow well. TwrShadow was changed from a TRUE/FALSE flag to an integer input in the dev branch of OpenFAST, i.e.: 0 TwrShadow - Calculate tower influence on wind based on downstream tower shadow (switch) {0=none, 1=Powles model, 2=E...
by Jason.Jonkman
Tue May 11, 2021 9:30 am
Forum: Computer-Aided Engineering Software Tools
Topic: FAST theory manual
Replies: 364
Views: 77655

Re: FAST theory manual

Sent.
by Jason.Jonkman
Tue May 11, 2021 7:16 am
Forum: Computer-Aided Engineering Software Tools
Topic: VTK output to binary output
Replies: 16
Views: 1431

Re: VTK output to binary output

Dear Tianhui.Liu, Yes, I recommend you use ParaView for the OpenFAST visualization output. You can find some introductory material on using ParaView to view OpenFAST visualization output files here: https://github.com/OpenFAST/r-test/blob/main/glue-codes/openfast/5MW_Land_ModeShapes/vtk-visualizatio...
by Jason.Jonkman
Tue May 11, 2021 6:55 am
Forum: Rotor Aerodynamics
Topic: Printing the axial induction factor in FAST
Replies: 37
Views: 13578

Re: Printing the axial induction factor in FAST

Dear Ricardo, The AeroDyn outputs BbNnVUndx are the wind speeds taken directly from InflowWind, without modification. I expect the values differ from your prescribed value of 10.59 m/s due to a change in coordinate system The AeroDyn outputs BbNnVUndx are expressed in the local blade coordinate syst...

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